OBJECTIVE: To investigate the possible effects of recruitment maneuver (RM) imposing on extravascular lung water (EVLW) in patients with acute respiratory distress syndrome (ARDS). METHODS: Twenty patients with ARDS who were eligible for the study were randomized to two groups, one group of which received regular therapy+RM (RM group), and to the other group only regular therapy was given (control group). Mechanical ventilation of all the patients was performed on the principles of lung protective ventilation. RM was carried out in bi-level positive airway passage (BIPAP) mode, and repeated every 8 hours per day until on the 7th day or before weaning of mechanical ventilation. The treatment was same between the two groups except RM. Baseline data and the influencing factors of EVLW were all recorded, which included everyday EVLW, extravascular lung water index (EVLWI) after RM, respiratory mechanics, oxygenation parameters, central venous pressure (CVP), plasma colloid osmotic pressure (COP), dosage of corticosteroid and adrenergic drugs, 24-hour net fluid balance. RESULTS: EVLW and EVLWI in RM and control group showed a tendency of decrease with passage of time, but the difference between both groups had no statistical significance (all P>0.05). The comparisons between the influencing factors of the groups, consisting of CVP, COP, noradrenalin and hydrocortisone, had no significant difference either (all P>0.05). Dopamine dosage in RM group on the 4th day was smaller than that of control group (P<0.05). Net fluid balance in RM group on the 7th day was negative, whereas it was positive in control group (P<0.05). Mean airway pressure [Pmean, RM group (18.8+/-3.2) cm H(2)O (1 cm H(2)O=0.098 kPa) vs. control group (16.6+/-3.9) cm H(2)O] and lung quasi-static compliance [Cstat, RM group (36.5+/-14.5) ml/cm H(2)O vs. control group (29.3+/-12.0) ml/cm H(2)O] in RM group were higher than those in control group (both P<0.05). Cstat on the 5th day was higher than that on the 2nd and 3rd day in RM group (both P<0.05). But oxygenation index (PaO(2)/FiO(2)) showed no distinct difference between the groups (all P>0.05). CONCLUSION: RM for the patients with ARDS can merely improve lung mechanics without obvious effect on EVLW. Neither of the influencing factors involved in the study has impact on emergence and clearance of EVLW.